Magnetic latch calibration system



ril 7, 1959 c. l. CLAUSING 2,881,283 MAGNETIC LATCH CALIBRATION SYSTEMFiled April 28. 1958 I qnnnnnn I I I I 8b I l 20 I I 2;: 49 72b I -o u14 NVENTOR.

BY ALL 40' z (140.1716

United States Patent 2,881,283 MAGNETIC LATCH CALIBRATION SYSTEMChalliss I. Clausing, Collingswood, NJ., assignor to I-T-E CircuitBreaker Company, Philadelphia, Pa., a corporation of PennsylvaniaApplication April 28, 1958, Serial No. 731,346 6 Claims. (Cl. 200-93) Myinvention relates to a novel calibration system for magnetic latches ofthe type set forth in my copending application Serial No. 719,067, filedMarch 4, 1958, entitled Magnetic Latch System for High Speed CircuitBreakers, and assigned to the assignee of the instant invention.

Magnetic latch systems for circuit breakers as described in my abovenoted copending application are comprised of a magnetic structure whichis provided with controlling windings for energization of the magneticstructure so that it may seal an armature which is movable with respectto the magnetic structure. The armature is operatively connected to amovable circuit breaker contact whereby the circuit breaker contact willmove to a disengaged position when the armature is moved away from itscooperating magnetic structure. When the armature is sealed to themagnetic structure, the circuit breaker contact operatively connected tothe armature will be positioned and held in the engaged position.

In order to control the energization of the magnetic structure, apolarizing coil generates a magnetomotive force which is sufiicient tomaintain the armature sealed to the magnetic structure. A second windingwhich conducts the current of the circuit breaker is magneticallycoupled with the polarizing coil so that responsive to a predeterminedcurrent condition of the circuit breaker, the second winding or socalled bucking bar will generate a magnetomotive force to buck down themagnetomotive force of the polarizing coil so that the armature will bereleased from the magnetic structure and the circuit breaker contactsmay be disengaged.

In order to calibrate the magnetic latch so that the armature will bereleased under a predetermined bucking bar current condition, it hasbeen the practice to adjust the reluctance of the magnetic structure andthereby effect the cooperation between the magnetomotive forcesgenerated by the polarizing coil and the bucking bar. However, since themagnetic latch structure is normally connected to one terminal of thecircuit breaker, it is normally necessary to isolate the circuit breakerfrom the source in order to make adjustments in the trippingcharacteristics of the latch since physical access to the latch isrequired. Furthermore, the adjustment of the reluctance of the circuitis relatively inaccurate and it is diflicult to set it to closetolerances.

The principle of my invention is to provide an adjustable impedancemeans in the polarizing coil circuit which operates in cooperation withthe control of the reluctance of the magnetic circuit to achieveadjustable calibration of the magnetic latch tripping characteristics.More specifically, the reluctance of the magnetic circuit is firstadjusted while the circuit breaker is isolated from its source to setthe latch at some upper calibration level. Thereafter, calibration isachieved through control of the polarizing coil ampere-turns by means ofthe variable impedance which could be a rheostat. Accordingly, when itis necessary to recalibrate the magnetic latch tripping characteristics,the circuit breaker need not be isolated from the source and thevariable impedance may be operated from some conveniently locatedposition to control the tripping point of the circuit breaker.

In view of the foregoing, the primary object of my invention is toprovide a novel calibration system for magnetic latches.

Another object of my invention is to provide a novel calibration systemfor magnetic latches which may be safely operated while the circuitbreaker is closed.

A further object of this invention is to provide a novel and simplecalibration system for magnetic latches associated with high speedcircuit breakers which is simple in construction and may be remotelyoperated while the circuit breaker is still energized.

A further object of this invention is to provide a calibration systemfor high speed circuit breaker magnetic latches wherein the reluctanceof the magnetic latch structure is initially adjusted to set the upperlimit or the calibration required and the calibration is,thereafterachieved by control of the polarizing coil ampereturns.

These and other objects of my invention will become apparent from thefollowing description taken in conjunction with the drawings in which:

Figure 1 schematically illustrates the type of magnetic latch to whichmy invention may be applied.

Figure 2 shows the magnetic latch structure in conjunction with aschematically illustrated circuit breaker with the circuit breaker inits closed position.

Figure 3 is similar to Figure 2 and illustrates the latch with thecircuit breaker in its tripped position.

Figure 4 is based on Figures 2 and 3 where the mag netic latch is resetafter the automatic operation shown in Figure 3.

Figure 5 is a top view of the magnetic latch structure and specificallyillustrates the manner in which calibration by control of the magneticcircuit reluctance is achieved.

Figure 6 illustrates a first embodiment of my novel invention.

Figure 7 illustrates a second embodiment of my novel invention.

Referring now to Figure 1, the general latch structure is comprised of amagnetic structure 10 having a polarizing coil 12 thereon which isenergized from a D.-C. energizing source connected to terminals 14 and16. The magnetic circuit of magnetic structure 10 includes a gap ofrelatively high reluctance 18 and armature member 20 positioned acrossthe gap 18. Note that this high reluctance path is obtained in Figure 5by means of slots 18a, 18b and 180.

The flux due to polarizing coil 12 is normally sufficient to maintainthe armature 20 sealed thereto in the absence of any other flux source.However, a second flux source is provided by magnetic structure 22 whichcontains a so-called bucking bar 24 therein which carries the loadcurrent of the circuit breaker, or some portion of the load current ofthe circuit breaker.

Figure 5 more accurately shows the magnetic armature 22 as comprisinglegs 22a, 22b and 220. Legs 22a and 220 are adjustably supported fromsupport means 17 and 19 by pairs of screws 21 and 23 respectivelywhereby the air gaps between the legs 22a and 22c with respect tomagnetic structure 10 and leg 22b is controlled.

The bucking bar 24 will generate a magnetic flux in core 22 which willoperate to normally aid the flux in that portion of the magneticstructure 10 which includes armature 20. However, when there is a faulton the systern and the current through bucking bar 24 reverses, the fluxthrough the portion of the magnetic circuit including armature 20 willbe bucked down or shifted so that the armature 20 will be released.

assnass Similarly, this system can apply to forward current tripping.That-is, thecurrent -inthe buck-ing bar isal- Ways in a trippingdirection and actual tripping occurs when the current reaches apredetermined value.

One application of this ftyp of rnagnetic latch system is: set forth-inthe circuit breaker device ofFigures 2, 3 and 4. The circuit br'eaker iscomprised of a. stationary contact 26 and movable. contact28.Movablecontact 28 is carried by a conductive contact arm 30 whichoperates as bucking bar 24 which is pivoted at pivot point 32": and isbiased to a contact disengaged position by openingspring 34 which isconnected to the contact arm 30 at-one end andto a fixed point 36 at itsother end. Contact arm 30 is then connected toa-walkingbearn 38 throughconnecting linlc 40Jjwh'ere the walking beam 38' 'is pivotally supportedat pivot 42.'- Thelow'er-endofwalkin-g beam 38' then supports thearmatureZtI as described in Figure 1.

The magnetic structure isprovided with a protruding-support arm 44 whichis pivotally connected to the same pivot 42 that supports walking beam'38. The lower end of magnetic structure 10 is connected to the upper endof the toggle linkage including toggle links 46 and 48. The lower. endof toggle link 48 is rotatably driven by motor 50 in the manner setforth in my copending application Serial No. 660,970, filed May 22,1957, entitled High Speed Circuit Breaker, and assigned to the assigneeof the instant invention, to drive the toggle linkage 46-and 48- againstits normal bias to break to the left as caused by biasing spring 52,while the right-hand motion of'the toggle linkageis limited by the stopmember 54.

As was described in connection with Figures 1 and 5, the polarizing coil12 operates asa first flux source for magnet 10 of Figures 2,; 3 and 4while the second flux source, as best seen in Figure 5, includesmagnetic legs 22a, 22b and 22c which surround the movable contact arm 24which generates a flux in the structure 22.

In operation, when the armature 20is sealed to magnetic structure 10, asshown in Figure 2, the circuit breaker movable contact arm 30.will berigidly positioned to the left to maintain movable contact 28 inengagement with fixed contact 26' against the opening force of openingspring 34. If, however, the current through contact arm 30 reverses, thenet flux in magnetic structure 10 at the area where armature 20 issealed will be shifted or bucked so that the armature 20-will bereleased, as seen in Figure 3, to thereby unlatch movable contact arm 30which is pulled to the right by opening spring 34.

This operationthen allows the toggle including links 46 and 48 to bebroken to the left, as shown in Figure 4,-whereby the magnet 10 rotatesabout pivot point 42 and 'is brought into engagement with armature 20,at which time the armature will again seal itself to the magneticstructure. After such sealing, the motor 50 may be energized to drivetoggle link'48 clockwise whereby the complete magnet assembly includingmagnet 10 and; armature 29-will be driven counterclockwise so as todrive contact arm 30, to the left'and into engagement with stationarycontact 26 against the biasing force of spring 34.

In order to calibrate the tripping point of the magneticlatch, it has.been the practice to adjust the position offlegs 22aand 22p to thereby.adjust the reluctance of the magnetic circuit which includes the buckingbar 24.

As previously .described it is necessary to disengage the circuitbrealger from the source when this adjustment is tq be nadesince thepresencepf bucking bar 24 would adjusting; operation.

Inaccordance with theinstant invention, the reluctance of..z.themagnetic circuit, is p'readjusted whenthe circuitbreaker is.disconnected from the source of some maxi-- mum calibration level;Calibration of the magnetic latch sej operating personnel to substantialdanger during.

system, while the circuit is engaged, is then achieved by adjusting-theampere-turns-of-thepolarizing coil.

Thus, as is seen in Figure 6, a D.-C. circuit having terminals 60 and 62is connected in series with terminals 14 and 16 of polarizing coil 12and in series with a rheostat 64. The rheostat 64 may be positioned atany convenient point so as to be readily available for adjustment.

Accordingly, while the circuit breaker contacts are still closed, thetrip level of themagneticlatch maybe made more sensitiveby increasingthe resistance of rheostat 64 or less sensitive by decreasing thevresistance of rheostat 64.

The secondernbodiment of 'my invention is set forth in Figure 7 in whichcon ponents similar to those of Figure 6 are given similar identifyingnumerals. More specifically, the embodiment of Figure 7 illustrates mynovel invention in combination withthe magnetic latch control system; ofmy above noted copending application Serial No: 719,067;- Inthe'circuit'of Figure 7; an additional resistor-665is added in series withpolarizing coil 12 where the resistor 66 has a-normally closed relaycontact--68 associated therewith. Relaycontact 68 is schematicallyindicated bythe dotted line as operatively connected tothe'schematically illustrated circuit breaker contacts 70- so thatc0ntact 68-will open only after the circuit breaker'contacts Id-close.

Accordingly, prior-to closure of the circuit breaker contacts, theampere-turns of polarizing coil 12 willbe relatively high so that arelatively large seal-in force is available toseal the armature of themagnetic latch to its cooperating magnetic structure. When the circuitbreaker contacts-70 are closed; however, relay contacts 68open'tothereby'place resistor-66 in series with polarizing coil 12 so as todecrease the ampere-turns of polarizing coil-12 to a relatively lowholding value.

Clearly, inthe circuit of Figure 7,'the rheostat 64 will operate in themanner set forth in Figure 6 for precisely adjusting-thelevelofampere-turns of polarizing coil 12 while the'circuit breakercontacts 70 are engagedso as to accurately adjust the calibration of themagnetic latch in any desired manner.

In the foregoing, I "have described my invention only inconnection withpreferred embodiments thereof. Many variations and -modifications oftheprinciples of my invention within the scope of the description hereinare obvious. Accordingly, I prefer to be bound not by the specificdisclosure herein but only-bythe appending claims.

I claim:

1. In a high speed magnetic latch system for a circuit breaker; amagnetic structure, an armature, and a first and second winding forgenerating magnetomotive force in said magnetic structure; said armaturebeing movable into and out of a magnetically-sealed position withrespect to saidmagneticstructure; said first winding being connected toa-source-of D.-C. voltage for supplying a first magnetomotive force tosaid magnetic structure; said second winding conducting acurrentfunctionally related to the current carried by said circuit breaker andsupply-,

ing a second magnetornotive force to said magnetic structure; saidsecond magnetomotive force being directed to, oppose said firstmagnctomotive force in at least the area of said magnetic structurereceiving said armature; said magnetic structure having adjustablecomponents for adjusting the reluctance of at least a portion of saidmag:

netic structure, the adjustment of said reluctance of said magneticstructure adjusting the relative effectiveness of said first and secondwindings in maintaining said, arms ture sealed to said-magneticstructure; said first winding" and said source of DQ-Clvoltage having anadjustable impedance means connected in circuit relation therewith;adjustment'of said impedance means controlling the am pere-turnss'upplied to said first winding and further ad-- justing the relativeefiectivenes sofsaid first and second windings in maintaining saidarmature sealed to said magnetic structure.

2. In a high speed magnetic latch system for a circuit breaker; amagnetic structure, an armature, and a first and second winding forgenerating magnetomotive force in said magnetic structure; said armaturebeing movable into and out of a magnetically sealed position withrespect to said magnetic structure; said first winding being connectedto a source of D.-C. voltage for supplying a first magnetomotive forceto said magnetic structure; said second winding conducting a currentfunctionally related to the current carried by said circuit breaker andsupplying a second magnetomotive force to said magnetic structure; saidsecond magnetomotive force being directed to oppose said firstmagnetomotive force in at least the area of said magnetic structurereceiving said armature; said magnetic structure having adjustablecomponents for adjusting the reluctance of at least a portion of saidmagnetic structure, the adjustment of said reluctance of said magneticstructure adjusting the relative effectiveness of said first and secondwindings in maintaining said armature sealed to said magnetic structure;said first winding having an adjustable resistor connected in seriestherewith; adjustment of said adjustable resistor varying theampere-turns of said first Winding to thereby provide calibrationadjustment for said magnetic latch system independently of saidadjustment of the reluctance of said magnetic structure.

3. In a high speed circuit breaker; a relatively fixed contact and arelatively movable contact movable into and out of engagement with saidrelatively fixed contact; a magnetic latch means for latching saidcircuit breaker contacts in engagement; said magnetic latch meansincluding a magnetic structure, an armature, a polarizing coil and abucking coil; said polarizing coil and said bucking coil being wound onsaid magnetic structure; said armature being movable into and out of amagnetically sealed position with respect to said magnetic structure;said armature being operatively connected to said circuit breakermovable contact to latch said contact in its engaged position when saidarmature is sealed to said magnetic structure, and to unlatch saidcontact when said armature is moved away from its said sealed position;said polarizing coil having an energizing circuit associated therewith;said energizing circuit being constructed to energize said polarizingcoil to cause said polarizing coil to generate a relatively large numberof ampere-turns to circulate from said magnetic structure to saidarmature when said armature is being moved towards its said magneticallysealed position and said movable circuit breaker contact is moved towardits said engaged position; said energizing circuit decreasing the numberof ampere-turns generated by said polarizing coil after said armature isin its said magnetically sealed position to a level sufiicient tonormally maintain said armature in said magnetically sealed position;said bucking coil being operable responsive to fault conditions to buckdown the ampere-turns sealing said armature to said magnetic structureto thereby unlatch said movable circuit breaker contact; said energizingcircuit further having an adjustable resistor associated therewith toadjust the ampere-turns supplied to said polarizing coil when saidcircuit breaker contacts are closed.

4. In a high speed circuit breaker; a relatively fixed contact and arelatively movable contact movable into and out of engagement with saidrelatively fixed contact; a magnetic latch means for latching saidcircuit breaker contacts in engagement; said magnetic latch meansincluding a magnetic structure, an armature, a polarizing coil and abucking coil; said polarizing coil and said bucking coil being wound onsaid magnetic structure; said armature being movable into and out of amagnetically sealed position with respect to said magnetic structure;said armature being operatively connected to said circuit breakermovable contact to latch said contact in its engaged position when saidarmature is sealed to said magnetic structure, and to unlatch saidcontact when said armature is moved away from its said sealed position;said polarizing coil having an energizing circuit associated therewith;said energizing circuit being constructed to energize said polarizingcoil to cause said polarizing coil to generate; ampere-turns tocirculate from said magnetic structure to said armature for magneticallysealing said armature to said magnetic structure and maintain saidcircuit breaker movable contact in its engaged position; said buckingcoil being operable responsive to fault conditions to buck down theampere-turns sealing said armature to said magnetic structure to therebyunlatch said movable circuit breaker contact; said energizing circuitfurther having an adjustable resistor associated therewith to adjust theampere-turns supplied to said polarizing coil when said circuit breakercontacts are closed.

5. In a magnetic latch structure for circuit breakers; said magneticlatch structure including a first magnetic structure, a second magneticstructure, an armature, a polarizing winding for said first magneticstructure and a circuit breaker current responsive winding for saidsecond magnetic structure; said armature being movable into and out ofmagnetically sealed relationship with respect to said first magneticstructure at a predetermined portion thereof; said polarizing windinghaving a first source of ampere-turns associated therewith forgenerating a magnetomotive force in said first magnetic structure forsealing said armature to said predetermined portion of said firstmagnetic structure; said second magnetic structure being positioned toinclude said predetermined portion of said first magnetic structure inits magnetic circuit; said circuit breaker current responsive windinggenerating a magnetomotive force in the magnetic circuit of said secondmagnetic structure to normally aid said magnetomotive force of saidfirst magnetic structure in sealing said armature to said first magneticstructure, reversal of current in said circuit breaker currentresponsive winding operating to decrease the net magnetomotive forcesealing said armature to said first magnetic structure; a variableresistance; said variable resistance being connected in circuit relationwith said polarizing coil to control the ampere-turns supplied to saidpolarizing coil by said source of ampere-turns; adjustment of saidvariable impedance adjusting the point at which said armature will bereleased from said first magnetic structure responsive to reversal ofcurrent in said circuit breaker current responsive winding.

6. In a magnetic latch structure for circuit breakers; said magneticlatch structure including a first magnetic structure, a second magneticstructure, an armature, a polarizing winding for said first magneticstructure and a circuit breaker current responsive winding for saidsecond magnetic structure; said armature being movable into and out ofmagnetically sealed relationship with respect to said first magneticstructure at a predetermined portion thereof; said polarizing windinghaving a first source of ampere-turns associated therewith forgenerating a magnetomotive force in said first magnetic structure forsealing said armature to said predetermined portion of said firstmagnetic structure; said second magnetic structure being positioned toinclude said predetermined portion of said first magnetic structure inits magnetic circuit; said circuit breaker current responsive windinggenerating a magnetomotive force in the magnetic circuit of said secondmagnetic structure to normally aid said magnetomotive force of saidfirst magnetic structure in sealing said armature to said first magneticstructure, reversal of current in said circuit breaker currentresponsive winding operating to decrease the net magnetomotive forcesealing said armature to said first magnetic structure; said magneticcircuit of said second magnetic structure having an adjustable membertherein for adjusting the reluctance of said magnetic circuit; avariable resist- '7 ance; said; variable resistance beinggconnectedpincircuit relation with.lsaidpolarizing coihto control; the ampere= turnssupplied, to said pplarizing; coils by saidysource of ampere-turns;adjustment of saidvariable impedanccadjusting the-ppint, at, vwhich saidarmature. will; be released from said first magnetic structureresponsive to reversal of; current in said, circuit breaker current.responsive windinggsaid. reluctance of. said magnetic circuit beingadjusted while said circuit breaker associated with said magneticlatchwis disconnected vfrom its source; said variable resistance :beingadjustablezwhile said circuit breaker 5 is connected' to its; source;

7 Nos references cited.

